Battery separator for extending the cycle life of a battery

ABSTRACT

A battery separator for extending the cycle life of a battery has a separator and a conductive layer. The conductive layer is disposed upon the separator. The conductive layer is adapted to be in contact with the positive electrode of the battery thereby providing a new route of current to and from the positive electrode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application claiming the benefit ofco-pending application Ser. No. 15/389,938, filed Dec. 23, 2016, whichis a continuation of U.S. application Ser. No. 11/535,701 filed Sep. 27,2006, and Issued as U.S. Pat. No. 9,564,623 on Feb. 7, 2017, thereferences which are hereby incorporated herein.

FIELD OF INVENTION

The instant application relates to battery separators used in secondarybatteries.

BACKGROUND OF THE INVENTION

A battery separator is a component that divides, or “separates”, thepositive electrode from the negative electrode within a battery cell. Abattery separator has two primary functions. First, a battery separatormust keep the positive electrode physically apart from the negativeelectrode in order to prevent any electronic current passing between thetwo electrodes. Second, a battery separator must permit an ionic currentbetween the positive and negative electrodes with the least possibleresistance. A battery separator can be made out of many differentmaterials, but these two opposing functions have been best met by abattery separator being made of a porous nonconductor.

An important parameter for describing a battery is the achievable numberof cycles, or the cycle life of the battery. The cycle life indicateshow often a battery can be charged and discharged repeatedly before alower limit of the capacity is reached, or a failure. Batteries with acycle life include all secondary batteries, or batteries that arecapable of being recharged several times. There are many secondarybatteries, including, but not limited to, lead-acid batteries. Foreconomical and ecological reasons, batteries with a high cycle life arepreferred.

Many batteries have a low cycle life, or fail, due to deterioration ofthe positive electrode conductor. The positive electrode conductor,usually in the form of a grid in a lead-acid battery, deteriorates fromcorrosion during the electrochemical process. The positive electrodeconductor corrodes faster than the negative electrode conductor becauseof the greater effects of the electrochemical process on the positiveelectrode. The more current flowing through the positive electrodeconductor, the faster the positive electrode conductor deteriorates. Thepositive electrode conductor is a critical element of a battery as itprovides the means for electrical current to flow to and from thepositive electrode. Thus, when the positive electrode conductordeteriorates, electrical current to and from the battery deteriorates.This deterioration causes the battery power to deteriorate, which inturn leads to battery failure.

Therefore, there is a need for extending the cycle life of a battery.More specifically, there is a need for extending the life of thepositive electrode conductor to achieve extended cycle life of thebattery.

SUMMARY OF THE INVENTION

The instant invention is a battery separator for extending the cyclelife of a battery. The battery separator has a separator and aconductive layer. The conductive layer is disposed upon the separator.The conductive layer is adapted to be in contact with the positiveelectrode of the battery thereby providing a new route of current to andfrom the positive electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustrating the invention, there is shown in thedrawings a form that is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIG. 1 is a fragmentary cross-sectional view of a battery with oneembodiment of the battery separator of the present invention.

FIG. 2 is an isometric view of one embodiment of the battery separatorof the present invention.

FIG. 3 is a line graph of the results of test 1.

FIG. 4 is a line graph of the results of test 2.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, wherein like numerals indicate like elements,there is shown in FIG. 1 an embodiment of a battery separator 10 forextending the cycle life of a battery 12. Battery 12 may be any type ofbattery. More specifically, battery 12 may be any type of battery thatmay be susceptible to electrode conductor deterioration. Battery 12 maybe a secondary battery. For example, battery 12 may be a lead-acidbattery (as shown in FIG. 1).

At least one battery separator 10 may be included in battery 12 (seeFIG. 1). Preferably, one battery separator 10 may be included in eachcell 24 of battery 12. Battery separator 10 may be for preventing anyelectronic current from passing between a positive electrode 16 and anegative electrode 17 while allowing ionic current to flow betweenpositive electrode 16 and negative electrode 17. In addition, batteryseparator 10 may be for extending the cycle life of battery 12 byproviding a new route of current to and from positive electrode 16.Battery separator 10 may also extend the cycle life of battery 12 byfunctioning as a positive electrode conductor when the conductivecapability of positive electrode conductor 18 deteriorates. Batteryseparator 10 may be made of any known battery separator materials,including, but not limited to, any porous nonconductor. Batteryseparator 10 may be any size or shape, including, but not limited to,flat or having ribs 22. Preferably, battery separator 10 may have ribs22 (see FIG. 2). Battery separator 10 may include a conductive layer 14.

Conductive layer 14 may be disposed on battery separator 12 (see FIG.2). Conductive layer 14 may be adapted to be in contact with positiveelectrode 16 of battery 12 (see FIG. 1). Conductive layer 14 may be forproviding a new route of current to and from positive electrode 16.Conductive layer 14 may be made of any conductive material, including,but not limited to, lead, gold, antimony, arsenic, zinc, barium,beryllium, lithium, magnesium, nickel, aluminum, silver, tin, andcombination alloys thereof, or carbon fibers, graphite, carbonnanotubes, or buckyballs. The carbon nanotubes or buckyballs might bedispersed in a medium with a binder and painted on battery separator 10.Conductive layer 14 may be made of any conductive material that is morecorrosion resistant than positive electrode conductor 18, thus, allowingconductive layer 14 to function as the positive electrode conductor 18when the conductive capability of the positive electrode conductor 18deteriorates. Conductive layer 14 may be a lead based alloy with 0.8% to1.17% tin, and greater than zero (0) to 0.015% silver. Conductive layer14 may be a lead-based alloy with 0.02% to 0.06% calcium, 0.3% to 3%tin, and 0.01% to 0.05% silver. Conductive layer 14 may be made into anyform, including but not limited to, a strip, a screen, a foil, a thread,a wire, a coating, etc. Conductive layer 14 may be any thickness,including, but not limited to, a thickness of three (3) micro meters.Conductive layer 14 may be disposed upon battery separator 10 by anymeans, including, but not limited to, adhesives, hot melting, painting,etc.

Ribs 22 may be included on battery separator 10. Ribs 22 may be formaintaining a maximum distance between the positive electrode 16 and thebattery separator 10. Ribs 22 may also be for achieving the desiredelectrolyte distribution in battery 12. Ribs 22 may be of any shape(straight, angled, waves, etc.) or form (triangular, circular, square,etc.). Ribs 22 may include tips 26.

Tips 26 may be a component of ribs 22. Tips 26 may be the distal ends ofeach rib 22. Tips 22 may be for providing a location for conductivelayer 14 to be disposed on battery separator 10 that allows conductivelayer 14 to be in contact with positive electrode conductor 16. Morespecifically, tips 22 may be for providing a specific location forconductive layer 14 to be in contact with positive electrode conductor16, which allows conductive layer 14 to be made out of the least amountof material for economical purposes.

For example, as shown in FIGS. 1-2, battery separator 10 may be made ofa porous nonconductor and have ribs 22 with tips 26. Conductive layer 14may be made of a fine silver powder dispersed in a solvent and paintedonto the tips 26 of ribs 22. Battery separator 10 may be used as theseparator of each cell 24 of battery 12.

In operation, battery separator 10 may perform the functions of abattery separator. Meaning, battery separator 10 may keep the positiveelectrode 16 physically apart from the negative electrode 17 in order toprevent any electronic current from passing between the two electrodes,and battery separator 10 may allow ionic current to flow between thepositive electrode 16 and the negative electrode 17. These functions mayallow the electrochemical process to take place and may force theelectrical current to flow from positive electrode conductor 18 tonegative electrode conductor 19, thus, allowing battery 12 to provideenergy.

Battery separator 10 may also provide extended cycle life for battery12. Extended cycle life may be accomplished through conductive layer 14.Conductive layer 14 may provide two ways of extending the cycle life forbattery 12.

First, because conductive layer 14 may be adapted to contact thepositive electrode 16 of battery 12 and conductive layer 14 may be madeout of a conductive material, conductive layer 14 may act as a secondpositive electrode conductor. This means that conductive layer 14 mayprovide a new route of current to and from positive electrode 16. Thisnew route of current through conductive layer 14 may reduce the amountof current through positive electrode conductor 18. Accordingly, therate that positive electrode conductor 18 deteriorates may be reduced.Thus, conductive layer 14 may extend the cycle life of battery 12.

Second, because conductive layer 14 may be adapted to be in contact withpositive electrode 16 providing a new route of current to and frompositive electrode 16, and because conductive layer 14 may be morecorrosive resistant than positive electrode conductor 18, conductivelayer 14 may function as positive electrode conductor 18 when theconductive capability of positive electrode conductor 18 deteriorates.This means that when a control battery fails due to the positiveelectrode conductor deteriorating, battery 12 with battery separator 10may not fail because conductive layer 14 may function as positiveelectrode conductor 18.

Thus, battery separator 10, and more specifically, conductive layer 14on battery separator 10, may provide two ways of extending the cyclelife of battery 12.

Test 1

One three-plate cell was constructed using various alternatives to makethe ends of the ribs conductive. The following are descriptions of thevarious ideas used:

Cell A used strips of thin pure lead attached to the tips of the ribswith adhesive.

Cell B used aluminum foil attached to the tips of several outer ribsusing hot melt.

Cells C1 and C2 used Aluminum foil that was attached to the tips of theribs with hot melt, with a punctured solid layer of foil in the centerof the separator. Two different ideas for evaluating the foilsperformance were used, one being with large “windows” and the other withsmall slits in the foil layer, thus, allowing electrolyte to flowfreely.

Cell D was the control material for the test.

Cell E used Silver paint (fine silver powder dispersed in a solvent,used for coating SEM samples) that was painted onto the tips of the ribsof the separator. Roughly 1 g of silver powder was applied to theseparator, in a layer of approximately twenty (20) micro meters.

These cells were formed and subjected to the following cycling regime:Discharged at 10 A to 1.65V; Charged at 2.50V (10 A limit) to 120% Ahremoved; Discharged at 5 A to 1.65V; Charged at 2.50V (10 A limit) to120% Ah removed; Discharged at 1 A to 1.65V; Charged at 2.50V (10 Alimit) to 120% Ah removed; and Charged at 1 A for 100 hours. This cyclewas repeated until the capacity fell below 50% of initial capacity.

A chart showing the results of the first test is shown in FIG. 3. InFIG. 3 the y-axis represents the Percentage of Cycle 1 Capacity, and thex-axis represents the Cycle Number.

As shown from the result of test 1, a battery separator with aconductive layer added to it may extend the cycle life of a battery. Thecell with the silver paint added to the separator lasted twice as longas the other alternatives, including the control.

Test 2

As a result of the work conducted and results achieved in test 1, asecond test was set up to verify the results of the first test (see FIG.4). For this test, a total of six complete batteries were built; threeas controls and three with battery separators with silver on the tips ofthe ribs. These batteries were subsequently tested via the hightemperature (75° C.) SAE J-240 life test, with the followingmodification made: As the batteries were made in-house and did not havestandard ratings or intercell connectors, the reserve capacity wasmeasured instead of a discharge at the CCA rate.

A chart detailing the results of the second test is shown in FIG. 4. InFIG. 4, the y-axis represents the Capacity in minutes and the x-axisrepresents the Week Number. The control batteries are represented byreference letter A, and the Test batteries are represented by referenceletter B.

As a result of test 2, the batteries with the silver painted on the ribswere confirmed to last longer than the control batteries.

Upon reviewing the results of the two battery tests conducted, batteryseparator 10 shows results for extending the cycle life of a battery.Additionally, capacity of a battery with a battery separator accordingto the instant invention may be higher than control batteries.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicated in the scope of the invention.

We claim:
 1. A lead acid battery comprising: a positive electrode; anegative electrode; a non-conductive separator comprising a porousmembrane with ribs disposed thereon; said ribs having rib tips disposedon a rib surface that faces away from said porous membrane; and aconductive layer disposed between and in direct contact with said ribtips and said positive electrode, said conductive layer being made of aconductive material being selected from the group consisting of lead,gold, antimony, arsenic, tin, and combination alloys thereof, carbon,carbon fibers, graphite, carbon nanotubes, buckyballs; and a combinationthereof.
 2. The battery separator of claim 1, wherein said ribs beingstraight, angled, or wavy.
 3. The battery separator of claim 1 whereinsaid conductive layer being strips.
 4. The battery separator of claim 1,wherein said conductive layer being a screen.
 5. The battery separatorof claim 1, wherein said conductive layer being a foil.
 6. The batteryseparator of claim 1, wherein said conductive layer being a thread. 7.The battery separator of claim 1, wherein said conductive layer being awire.
 8. A lead acid battery comprising: a positive electrode; anegative electrode; a non-conductive separator comprising a porousmembrane with ribs disposed thereon; said ribs having rib tips disposedon a rib surface that faces away from said porous membrane; and aconductive layer disposed between and in direct contact with said ribtips and said positive electrode, said conductive layer being made of aconductive material being selected from the group consisting of lead,gold, antimony, arsenic, tin, and combination alloys thereof.
 9. A leadacid battery comprising: a positive electrode; a negative electrode; anon-conductive separator comprising a porous membrane with ribs disposedthereon; said ribs having rib tips disposed on a rib surface that facesaway from said porous membrane; and a conductive layer disposed betweenand in direct contact with said rib tips and said positive electrode,said conductive layer being made of a conductive material being selectedfrom the group consisting of carbon, carbon fibers, graphite, carbonnanotubes, buckyballs, and a combination thereof.
 10. A lead acidbattery comprising: a positive electrode; a negative electrode; anon-conductive separator comprising a porous membrane with ribs disposedthereon; said ribs having rib tips disposed on a rib surface that facesaway from said porous membrane; and a conductive layer disposed betweenand in direct contact with said rib tips and at least one saidelectrode, said conductive layer being made of a conductive materialbeing selected from the group consisting of lead, gold, antimony,arsenic, tin, and combination alloys thereof, carbon, carbon fibers,graphite, carbon nanotubes, buckyballs; and a combination thereof. 11.In a system or vehicle, the improvement comprising the lead acid batteryof claim
 1. 12. In a system or vehicle, the improvement comprising thelead acid battery of claim
 8. 13. In a system or vehicle, theimprovement comprising the lead acid battery of claim
 9. 14. In a systemor vehicle, the improvement comprising the lead acid battery of claim10.